An ancient mangrove forest with trees growing up to 40 meters high has been discovered in what is now Panama, 20 million years after a volcanic mudflow drowned it, new research shows.

Researchers first discovered the fossils during a geological expedition on Barro Colorado Island (BCI) in 2018. The island is located in Panama’s artificial lake, Gatun, through which thousands of ships pass through the Panama Canal each year. BCI was once part of a rugged landscape that was partially flooded in 1913 when engineers dammed the Chagres River to build a canal, and was set aside as a nature reserve in 1923. Today, BCI rainforests are among the most intensively studied in the world.

“We never thought there would be fossil wood at BCI,” said Carlos Jaramillo, a Smithsonian geologist and one of the study’s authors. “Nobody reported on them,” he said. Institute for Tropical Research in Panama. , he told LiveScience in an email. Jaramillo said the fossils were “difficult to distinguish from other rotten trees in the forest” because they resembled rotting logs.

Despite their appearance, the mangrove fossils are actually quite well preserved, Jaramillo said. This is because a volcanic eruption about 23 million years ago during the Early Miocene (23 million to 5.3 million years ago) buried trees, slowing decomposition and freezing the landscape in time.

“Fossil wood samples, also known as petrified wood, preserve a wealth of information,” study lead author Camila Martínez Águilon, a paleoecologist at EAFIT University in Colombia, told Live Science in an email. The cellular structure has been mineralized and preserved intact over the ages, offering researchers “a rare and wonderful opportunity to travel back in time,” Martínez Águilon said.

Researchers examined 121 fossilized tree samples exposed in a small stream at BCI and found that 50 of them belonged to a previously unknown species. Sonneratioxylon barrocoloradoensis . The newly discovered fossil species resemble mangrove trees growing in Southeast Asia; Australasia, a region that includes Australia, New Zealand, and some nearby islands; Martinez Aguillon said parts of tropical Africa exist today.

But the ancient forest was much taller than modern mangroves, according to a study published in the March 2024 issue of the journal Paleogeography, Paleoclimatology, Paleoecology. While the tops of most living mangroves reach about 43 feet (13 meters), S. barrocoloradoensis It grew to about 82 feet (25 m) and could climb up to 130 feet (40 m).

Ancient trees likely developed the same survival strategies that mangroves use today, preferring brackish waters over highly salty ocean waters, Jaramillo said. The forest surrounded a narrow peninsula connecting modern central Panama to North America. Formation of the Isthmus of PanamaSomewhere between 23 and 3 million years ago.

The mangrove fossils were all in a similar state of preservation; This led researchers to believe that the forest was destroyed by a single volcanic eruption that filled the land with mud. Since researchers first discovered wood fossils on Barro Colorado Island, “people are finding a lot more all over the island,” Jaramillo said.